Gastric pseudocyst drainage and stent delivery system for use therein

ABSTRACT

Method for draining pseudocysts and stent delivery system for use therein. In one embodiment, the system comprises an inner catheter provided with a pair of longitudinal lumens. A guide wire is slidably disposed in one lumen, and a retractable needle is slidably disposed in the other lumen. A self-expandable stent is coaxially mounted around the inner catheter near its distal end, and an outer catheter is coaxially mounted around the inner catheter and the stent, the outer catheter being adapted for axial movement relative to the inner catheter and being dimensioned to maintain the stent in a compressed state. In use, an endoscope is intraorally introduced into a patient&#39;s stomach, and the distal end of the system is inserted therethrough. The needle is advanced to form perforations in the stomach and pseudocyst. The inner catheter is then inserted through the perforations, and the outer catheter is retracted, allowing the stent to expand and interconnect the stomach and pseudocyst. The endoscope and the rest of the delivery system are then withdrawn from the patient.

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to gastric pseudocystdrainage and relates more particularly to a novel method for draininggastric pseudocysts and to a novel stent delivery system for use in saidmethod.

[0002] A gastric or pancreatic pseudocyst is an aggregation of tissue,fluid, debris, pancreatic enzymes and blood that often develops in theperitoneal cavity after the onset of acute pancreatitis. Although manypseudocysts resolve themselves spontaneously, some pseudocysts becomequite large and require treatment due to the unwanted pressure theyexert against the stomach and/or neighboring organs.

[0003] One approach to treating gastric pseudocysts involves surgery andtypically comprises (i) cutting through the abdominal wall of thepatient to permit access to the pseudocyst through the abdominal wall,(ii) perforating or puncturing the pseudocyst, (iii) inserting adrainage tube into the pseudocyst through the perforation to allow thecontents of the pseudocyst to empty through the drainage tube to a pointexternal to the patient, (iv) removing the drainage tube from thepatient once the pseudocyst has been emptied, and (v) repairing theabdominal wall.

[0004] As can readily be appreciated, the surgical approach describedabove is invasive and has easily identifiable drawbacks associatedtherewith, such as an appreciable risk of infection.

[0005] More recently, an endoscopic approach to treating gastricpseudocysts has been devised. This approach is less invasive thansurgery and typically involves inserting an endoscope through thepatient's mouth and into the patient's stomach. The endoscope is firstused to visually locate the pseudocyst on the opposite side of thestomach wall. A needle or sphincterotome is then extended through thedistal end of the endoscope to perforate both the stomach wall and thepseudocyst. A contrast agent delivered through the endoscope is theninjected into the pseudocyst, and a cystogram is endoscopicallyperformed to confirm entry into a pseudocyst (as opposed to entry intothe peritoneal cavity). Following confirmation of entry into apseudocyst, a guide wire is advanced through the endoscope and into thepseudocyst. Next, a balloon catheter is advanced through the endoscopeand over the guide wire into the pseudocyst. The balloon is dilated toenlarge the perforations in the pseudocyst and the stomach and is thendeflated and withdrawn. A plurality of straight endobiliary tubes offixed diameter (each approximately 10 Fr) are then endoscopicallyimplanted across the pseudocyst and stomach perforations to allow thecontents of the pseudocyst to drain into the stomach, said biliary tubesbeing arranged in a side-by-side fashion and being implanted one at atime. The endoscope is then removed from the patient. When drainage iscomplete (typically within a few weeks), the endoscope is reintroducedinto the patient, and the biliary tubes are withdrawn from the patientthrough the endoscope using a snare.

[0006] Although the aforementioned endoscopic approach has certainadvantages over the surgical approach described above, the foregoingendoscopic approach still suffers from certain drawbacks. One suchdrawback is that the biliary tubes presently used are relatively smallin diameter and have a tendency to become occluded during use. Suchocclusion is due, in part, to the inward radial pressure exerted by thepseudocyst and stomach walls against the tubes, and is due, in part, tothe viscous nature of the materials conveyed within the small diametertubes. Another drawback is that the biliary tubes used are susceptibleto dislodgement from the pseudocyst and/or the stomach because they arestraight and lack anchoring means. Still another drawback is that asecond endoscopic procedure is needed to remove the biliary tubes fromthe patient following drainage of the pseudocyst. Still yet anotherdrawback is that a multitude of different catheters or other devicesmust be sequentially inserted into the endoscope to enable the varioussteps outlined above to be performed.

SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide a noveltechnique for draining gastric pseudocysts.

[0008] It is another object of the present invention to provide atechnique as described above that overcomes at least some of theabove-described shortcomings associated with existing techniques fordraining gastric pseudocysts.

[0009] Therefore, in furtherance of the above and other objects to bedescribed or to become apparent from the description below, there isprovided herein a method of draining a pseudocyst present within apatient, said method comprising, according to one aspect, the steps of(a) providing a stent, said stent being transformable from anon-expanded state of comparatively lesser diameter to an expanded stateof comparatively greater diameter, said stent having a first end and asecond end; (b) delivering said stent in said non-expanded state to apseudocyst located within a patient; (c) inserting said first end ofsaid stent into the pseudocyst; and (d) transforming said stent fromsaid non-expanded state to said expanded state; (e) whereby thepseudocyst drains through said stent.

[0010] Preferably, the aforementioned method further comprises the stepsof inserting said second end of said stent into the stomach of thepatient whereby the pseudocyst drains through said stent into thestomach and, prior to said first end and second end inserting steps,forming a perforation in each of the pseudocyst and the stomach, whereinsaid first end inserting step comprises inserting said first end of saidstent through said perforations in the pseudocyst and the stomach.Moreover, the stent is preferably introduced into the stomach of thepatient intraorally.

[0011] The above-described stent may be a self-expandable stent or maybe a balloon-expandable stent. In the case of a self-expandable stent,said delivering step comprises maintaining said stent in saidnon-expanded state using a removable restraint, and said transformingstep comprises removing said removable restraint from said stent toallow said stent to self-expand. The self-expandable stent, which ispreferably made of a braided filamentary material, may be shaped toinclude a waist of comparatively lesser expanded diameter (e.g., 8-10mm) and a pair of cuffs on opposite ends of said waist of comparativelygreater expanded diameter (e.g., about 15 mm) or may have a uniformrelaxed diameter. The self-expandable stent may be made of abiocompatible nonabsorbable material, such as a metal or a plastic, ormay be made of a bioabsorbable material.

[0012] Where the stent is a balloon-expandable stent, saidballoon-expandable stent is preferably a covered balloon-expandablestent. In addition, said delivering step preferably comprises mountingsaid balloon-expandable stent, in said non-expanded state, over adeflated balloon catheter and then inserting said deflated ballooncatheter into a patient in the area of a pseudocyst. Said transformingstep preferably comprises inflating said deflated balloon catheter untilsaid balloon-expandable stent is transformed from said non-expandedstate to said expanded state.

[0013] Where the stent, whether self-expandable or balloon-expandable,is nonabsorbable, the method preferably further comprises the step ofendoscopically removing said stent with a snare after drainage of thepseudocyst is complete.

[0014] According to another aspect of the invention, there is provided amethod of draining a pseudocyst present within a patient, said methodcomprising the steps of (a) providing a double pigtail stent, saiddouble pigtail stent having a first end and a second end, each of saidfirst and second ends being transformable from a straightened state,when constrained, to a curled state, when relaxed; (b) coaxiallymounting said double pigtail stent over the distal end of a catheter,whereby each of said first and second ends is in said straightenedstate; (c) endoscopically introducing said double pigtail stent and thedistal end of said catheter through the mouth and into the stomach of apatient in the vicinity of a pseudocyst; (d) sliding said first end ofsaid double pigtail stent off the distal end of said catheter, throughthe stomach and into the pseudocyst, whereby said first end istransformed from said straightened state to said curled state; and (e)sliding said second end of said double pigtail stent off the distal endof said catheter into the stomach, whereby said second end istransformed from said straightened state to said curled state; (f)whereby the pseudocyst drains through said stent into the stomach.

[0015] Preferably, the aforementioned method further comprises, aftersaid endoscopic introducing step and before said sliding steps, the stepof forming a perforation in each of the stomach and the pseudocyst, saidfirst end sliding step comprising sliding said first end of said doublepigtail stent off the distal end of said catheter and through theperforations in the stomach and pseudocyst, respectively. In addition,the distal end of said catheter preferably includes a balloon, saidmethod further comprising, after said perforation forming step andbefore said sliding steps, the steps of inserting said balloon into saidperforations, then inflating said balloon, then deflating said balloonand withdrawing said balloon from said perforations. After drainage ofthe pseudocyst is complete, the foregoing double pigtail stent ispreferably endoscopically removed using a snare.

[0016] The present invention is also directed to a stent deliverysystem, said stent delivery system comprising, in a first embodiment,(a) an inner catheter, said inner catheter being provided with a firstlongitudinally extending lumen; (b) perforating means slidably disposedin said first longitudinally extending lumen; (c) an outer catheter,said outer catheter surrounding at least a portion of the length of saidinner catheter and adapted for axial movement relative to said innercatheter; and (d) a self-expandable stent, said self-expandable stentdisposed between said inner catheter and said outer catheter; (e)wherein said outer catheter is dimensioned to maintain saidself-expandable stent in a compressed state.

[0017] Preferably, the aforementioned self-expandable stent is coaxiallymounted over said inner catheter, said self-expandable stent being madeof braided filamentary material. Said self-expandable stent may be madeof nonabsorbable material or may be made of bioabsorbable material. Saidself-expandable stent may be shaped to have a uniform relaxed diameteror may be shaped to include a waist of comparatively lesser expandeddiameter and a pair of cuffs on opposite ends of said waist ofcomparatively greater expanded diameter.

[0018] The perforating means of the subject stent delivery systempreferably comprises a retractable needle. The inner catheter of saidstent delivery system is preferably provided with a second longitudinallumen, a guide wire being slidably disposed in said second longitudinallumen.

[0019] In a second embodiment, the stent delivery system of the presentinvention comprises (a) a catheter, said catheter having a proximal end,a distal end, a first lumen extending longitudinally through said distalend and a second lumen extending longitudinally and having a proximalend connected to a gas line and a distal end terminating in a balloonsection; (b) perforating means slidably disposed in said first lumen;and (c) a balloon-expandable stent coaxially mounted over said balloonsection of said catheter.

[0020] Preferably, the aforementioned balloon-expandable stent is aballoon-expandable covered stent. In addition, the above-described stentdelivery system preferably further comprises a sheath, said sheathsurrounding at least a portion of the length of said catheter and saidballoon-expandable stent and being adapted for axial movement relativeto said catheter. Said catheter preferably further comprises third andfourth lumens extending longitudinally through said distal end, saidthird lumen receiving a slidably mounted guide wire, said fourth lumenbeing connected at its proximal end to a line containing dye for use inperforming a cystogram.

[0021] In a third embodiment, the stent delivery system of the presentinvention comprises a stent delivery system comprising (a) a catheter,said catheter having a proximal end, a distal end, a first lumenextending longitudinally through said distal end, and a second lumenextending longitudinally and having a proximal end connected to a gasline and a distal end terminating in a balloon section; (b) perforatingmeans slidably disposed in said first lumen; and (c) a first pigtailstent coaxially and slidably mounted over said catheter proximal to saidballoon section.

[0022] Preferably, the aforementioned stent delivery system furthercomprises a pusher sleeve coaxially and slidably mounted over saidcatheter proximal to said first pigtail stent for pushing said firstpigtail stent off said distal end of said catheter. In addition, saidstent delivery system preferably further comprises a second pigtailstent coaxially and slidably mounted over said catheter proximal to saidballoon section and distal to said first pigtail stent. Said catheterpreferably further comprises third and fourth lumens extendinglongitudinally through said distal end, said third lumen receiving aslidably mounted guide wire, said fourth lumen being connected at itsproximal end to a line containing dye for use in performing a cystogram.

[0023] Additional objects, features, aspects and advantages of thepresent invention will be set forth, in part, in the description whichfollows and, in part, will be obvious from the description or may belearned by practice of the invention. In the description, reference ismade to the accompanying drawings which form a part thereof and in whichis shown by way of illustration specific embodiments for practicing theinvention. These embodiments will be described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and that structuralchanges may be made without departing from the scope of the invention.The following detailed description is, therefore, not to be taken in alimiting sense, and the scope of the present invention is best definedby the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are hereby incorporated into andconstitute a part of this specification, illustrate preferredembodiments of the invention and, together with the description, serveto explain the principles of the invention. In the drawings wherein likereference numerals represent like parts:

[0025]FIG. 1 is a side view of a first embodiment of a stent adapted foruse in draining a gastric pseudocyst in accordance with the teachings ofthe present invention;

[0026]FIG. 2 is a side view of a second embodiment of a stent adaptedfor use in draining a gastric pseudocyst in accordance with theteachings of the present invention;

[0027]FIG. 3 is a side view of a third embodiment of a stent adapted foruse in draining a gastric pseudocyst in accordance with the teachings ofthe present invention;

[0028]FIG. 4 is a side view of a first embodiment of a stent deliverysystem constructed according to the teachings of the present invention,said stent delivery system including the stent of FIG. 1;

[0029]FIG. 5 is a fragmentary schematic longitudinal section view of thestent delivery system of FIG. 4, showing the distal end thereof;

[0030] FIGS. 6(a) through 6(h) are fragmentary schematic views, partlyin section, illustrating how the stent delivery system of FIG. 4 may beused endoscopically to perform the gastric drainage method of thepresent invention;

[0031]FIG. 7 is a perspective view of a fourth embodiment of a stentadapted for use in draining a gastric pseudocyst in accordance with theteachings of the present invention;

[0032] FIGS. 8(a) and 8(b) are fragmentary side and fragmentaryschematic longitudinal section views, respectively, of a secondembodiment of a stent delivery system constructed according to theteachings of the present invention, said stent delivery system includingthe stent of FIG. 7;

[0033]FIG. 9 is a side view, broken away in part, of a fifth embodimentof a stent adapted for use in draining a gastric pseudocyst inaccordance with the teachings of the present invention;

[0034]FIG. 10 is a side view of a sixth embodiment of a stent adaptedfor use in draining a gastric pseudocyst in accordance with theteachings of the present invention; and

[0035] FIGS. 11(a) and (b) are fragmentary side and fragmentaryschematic longitudinal section views, respectively, of a thirdembodiment of a stent delivery system constructed according to theteachings of the present invention, said stent delivery system includingthe stent of FIG. 10.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0036] Referring now to FIG. 1, there is shown a side view of a firstembodiment of a stent adapted for use in draining a gastric pseudocystin accordance with the teachings of the present invention, said stentbeing represented generally by reference numeral 11.

[0037] Stent 11 is a self-expandable stent (i.e., tubularendoprosthesis) shaped to include a pair of cuffs 13-1 and 13-2 ofcomparatively large relaxed diameter (i.e., approximately 15 mm) and amidsection or waist 15 of comparatively small relaxed diameter (i.e.,approximately 8-10 mm). As will be seen below, waist 15 is adapted to beinserted through the perforations formed in a stomach and a pseudocyst,and cuffs 13-1 and 13-2 are adapted to engage the walls of the stomachand the pseudocyst, respectively, in order to prevent the longitudinaldisplacement of stent 11 relative thereto. Each of cuffs 13-1 and 13-2and waist 15 has a length of approximately 5-10 mm.

[0038] Although, in the present embodiment, stent 11 is made by braidingfilamentary material, it can readily be appreciated that stent 11 couldalternatively be made, for example, by coiling, crocheting or knittingfilamentary material or by any other suitable manufacturing process.Braiding may be preferred, however, since it is a comparativelyinexpensive manufacturing technique that results in a structurally soundproduct from an engineering standpoint. The filamentary material used tomake stent 11 is nonabsorbable and may be a metal filament, such as anitinol (a nickel/titanium alloy) wire, or may be a nonabsorbablepolymeric filament. A nonabsorbable polymeric filament may be preferredover a metal filament since stents made of metal wire often possesssharp ends, which may be injurious to a stomach wall. As can readily beappreciated, one can modify the radial self-expansion force exerted bystent 11 by correspondingly modifying the thickness of the filament usedto make stent 11 (i.e., the thicker the filament, the greater the radialself-expansion force).

[0039] Stent 11 may be coated with an antibiotic to prevent infection;alternatively, an antibiotic may be incorporated into the filamentarymaterial used to make stent 11.

[0040] Referring now to FIG. 2, there is shown a side view of a secondembodiment of a stent adapted for use in draining a gastric pseudocystin accordance with the teachings of the present invention, said stentbeing represented generally by reference numeral 31.

[0041] Stent 31 is similar in most respects to stent 11, the onlydifference between the two stents being that stent 31 is made from oneor more bioabsorbable materials including, but not limited to,homopolymers and copolymers of glycolide, lactide, ε-caprolactone andp-dioxanone, copolymers of glycolide and trimethylene carbonate, as wellas polyanhydrides and polyorthoesters. Additional examples ofbioabsorbable materials that may be used to make stent 31 are disclosedin pages 39-50 of Wound Closure Biomaterials and Devices, edited byChih-Chang Chu, J. Anthony von Fraunhofer and Howard P. Greisler,published by CRC Press, Inc. (1997), which is incorporated herein byreference.

[0042] As can readily be appreciated, one can alter the life span ofstent 31 as desired by modifying the type of bioabsorbable material usedin stent 31 and/or by modifying the thickness of the filamentarymaterial used to make stent 31. Preferably, stent 31 has a life span onthe order of about 3-6 weeks, which is generally the maximum amount oftime needed for a gastric pseudocyst to drain.

[0043] Referring now to FIG. 3, there is shown a side view of a thirdembodiment of a stent adapted for use in draining a gastric pseudocystin accordance with the teachings of the present invention, said stentbeing represented generally by reference numeral 51.

[0044] Stent 51 is similar in most respects to stent 11, the principaldifferences between the two stents being that stent 51 has a uniformdiameter along its length and may be made of either a nonabsorbablematerial or a bioabsorable material. As can readily be appreciated, whenstent 51 is implanted in a patient, the shape of stent 51 will tend toresemble that of stents 11 and 31 since the midsection of stent 51 willtend to be compressed by the stomach and pseudocyst walls whereas theends of stent 51 will tend to be less compressed and, therefore, morefree to expand to their relaxed states.

[0045] Referring now to FIGS. 4 and 5, there are shown side andfragmentary schematic longitudinal section views, respectively, of afirst embodiment of a stent delivery system constructed according to theteachings of the present invention, said stent delivery system beingrepresented generally by reference numeral 71.

[0046] System 71 comprises a flexible, inner catheter 73. A handle 75 isdisposed at the proximal end of catheter 73, and an enlarged tip 77 isdisposed at the distal end of catheter 73. A pair of parallel lumens79-1 and 79-2 extend longitudinally through catheter 73. A guide wire 80is removably received within lumen 79-1 and is adapted for use inpositioning system 71 at a desired position within a body lumen. Aretractable needle 81 is removably received within lumen 79-2 and isadapted for use in perforating the stomach and pseudocyst walls. (Needle81 may be replaced with a retractable knife or with a retractable,electrically-conductive cauterizing device, such as a needle-knifesphincterotome.)

[0047] System 71 also comprises a self-expandable stent, saidself-expandable stent being mounted over catheter 73 in a stretched orcompressed state proximally relative to tip 77. Although, in the presentembodiment, said self-expandable stent is stent 11, it can readily beappreciated that stent 11 may be replaced with stent 31, stent 51 or anyother suitable self-expandable stent. A space-filling jacket 83 issecured (e.g., by a friction-fit) to catheter 73 proximally relative tostent 11. Jacket 83 serves to prevent proximal sliding of stent 11during deployment.

[0048] System 71 further comprises a flexible, outer catheter 85.Catheter 85 coaxially surrounds much of the distal end of catheter 73 upto tip 77 and, additionally, coaxially surrounds and maintains stent 11in its stretched or compressed state. Catheter 85 is adapted for axialmovement relative to catheter 73, and a handle 87 is disposed at theproximal end of catheter 85 for use in axially moving catheter 85relative to catheter 73.

[0049] Referring now to FIGS. 6(a) through 6(h), there is illustratedthe manner in which system 71 may be used to drain a gastric pseudocyst.In FIG. 6(a), a gastric pseudocyst G is shown pressing inwardly againstthe exterior surface of a stomach wall W. In FIG. 6(b), the distal endof an endoscope E is inserted into the stomach (presumably through themouth of the patient) and is positioned in the vicinity of where stomachwall W is contacted by pseudocyst G. In FIG. 6(c), the distal end ofsystem 71 is advanced out through the distal end of endoscope E towardsthe distended portion of stomach wall W, the distal end of system 71being deflected 90° relative to the longitudinal axis of endoscope E byan elevator L pivotally mounted on endoscope E at its distal end. InFIG. 6(d), needle 81 is advanced from the distal end of system 71 toform perforations P1 and P2 in stomach wall W and pseudocyst G,respectively. Needle 81 is then retracted. In FIG. 6(e), the distal endof system 71 is advanced into pseudocyst G through perforations P1 andP2. Outer catheter 85 of system 71 is then retracted proximally, therebyallowing stent 11 to self-expand. Inner catheter 73 and endoscope E arethen retracted proximally, leaving stent 11 in place with cuffs 13-1 and13-2 engaging pseudocyst G and the stomach wall W, respectively, andwaist 15 extending therebetween through perforations P1 and P2. As shownin FIG. 6(f), with stent 11 in place, the contents of pseudocyst G arepermitted to drain into the stomach. This may take up to about 3-6weeks. As shown in FIGS. 6(g) and 6(h), when drainage is complete,endoscope E is reintroduced into the stomach (preferably via the mouth),and a snare S is advanced from the distal end of endoscope E to withdrawstent 11 from the patient.

[0050] It should be understood that the aforementioned procedure mayalso include an endoscopically-aided preliminary examination of thestomach and pseudocyst, as well as an endoscopically-aided cystogram ofthe type described above.

[0051] As can readily be appreciated, some of the advantages of usingstent 11, as compared to conventional endobiliary tubes, to draingastric pseudocysts are that (i) the expanded diameter of stent 11 islarger than the fixed diameter of an individual endobiliary tube (about8-10 mm vs. about 3-5 mm, respectively), thereby resulting in fasterdrainage and obviating the need for a plurality of drainage members tobe implanted; (ii) due to the anchoring action of cuffs 13-1 and 13-2,stent 11 is less likely to become longitudinally dislodged from apseudocyst and/or stomach than are endobiliary tubes; and (iii) due tothe radial expansion force exerted by stent 11, stent 11 is less likelyto become constricted by radially inward forces exerted by a pseudocystand/or stomach.

[0052] Bioabsorbable stent 31 has a further advantage over nonabsorbablestent 11 in that it does not require an additional endoscopic procedurefor its removal since it degrades on its own within a few weeks afterhaving been implanted in a patient. This is also advantageous for thereason that, within a few weeks after having been implanted in apatient, there is a tendency for stomach tissue to grow into anonabsorbable stent, thereby making its removal from a patient moredifficult and increasing the risk of injury to the patient.

[0053] Referring now to FIG. 7, there is shown a perspective view of afourth embodiment of a stent adapted for use in draining a gastricpseudocyst in accordance with the teachings of the present invention,said stent being represented generally by reference numeral 101.

[0054] Stent 101 is a balloon-expandable stent capable of beinginelastically expanded to a diameter of about 8-10 mm. Examples ofvarious balloon-expandable stents are disclosed in the following U.S.patents, all of which are incorporated herein by reference: U.S. Pat.No. 4,922,905, inventor Strecker, issued May 8, 1990; U.S. Pat. No.4,950,227, inventors Savin et al., issued Aug. 21, 1990; and U.S. Pat.No. 4,733,665, inventor Palmaz, issued Mar. 29, 1988. Although in thepresent embodiment, stent 101 is a mesh tube made of a ductile metal,stent 101 is not limited in structure or materials thereto.

[0055] Referring now to FIGS. 8(a) and 8(b), there are shown fragmentaryside and fragmentary schematic longitudinal section views, respectively,of a second embodiment of a stent delivery system constructed accordingto the teachings of the present invention, said stent delivery systembeing represented generally by reference numeral 121.

[0056] System 121 comprises a flexible catheter 123. A handle 125 isdisposed at the proximal end of catheter 123, and a tip 127 is disposedat the distal end of catheter 123. A plurality of parallel lumens 129-1through 129-3 extend longitudinally through catheter 123. A guide wire130 is removably received within lumen 129-1 and is adapted for use inpositioning system 121 at a desired position within a body lumen. Aretractable needle 131 is removably received within lumen 129-2 and isadapted for use in perforating the stomach and pseudocyst walls. (Needle131 may be replaced with a retractable knife, a retractablesphincterotome or the like.) Lumen 129-3 is coupled at its proximal endto a line 132 containing a dye of the type suitable for use inperforming a cystogram of the pseudocyst. A fourth lumen 133, which isconnected at its proximal end to a gas line 134, surrounds the distalends of lumens 129-1 through 129-3 and ends in a balloon section 135proximal to tip 127.

[0057] System 121 also comprises a balloon-expandable stent, saidballoon-expandable stent being coaxially arranged over balloon section135. Although in the present embodiment, said balloon-expandable stentis stent 101, it can readily be appreciated that otherballoon-expandable stents may also be suitable. (For example, stent 101may be replaced with the fabric covered balloon-expandable stent 141 ofFIG. 9. In fact, stent 141 may be preferred to stent 101 for gastricpseudocyst drainage for the reason that tissue growth into stent 141 ismade more difficult by the presence of cover 143. Consequently, removalof covered stent 141 from a patient may be less difficult than thecorresponding removal of uncovered stent 101.)

[0058] A sheath 151 coaxially surrounds much of the distal end ofcatheter 123 including stent 101. Sheath 151 is adapted for axialmovement relative to catheter 123, and a handle 153 is disposed at theproximal end of sheath 151 for use in axially moving sheath 151 relativeto catheter 123.

[0059] System 121 is used in much the same way as system 71 describedabove, stent 101 being deployed by (i) inserting the distal end ofsystem 121 through the perforations in the stomach and pseudocystpreviously created by needle 131, (ii) withdrawing sheath 151, (iii)expanding balloon section 135 and stent 101 until stent 101 reaches itsdesired diameter, (iv) deflating balloon section 135, and (v)withdrawing catheter 123.

[0060] One possible advantage of system 121 relative to system 71 isthat balloon section 135 of system 121 may be capable of creatingperforations of larger diameter in the pseudocyst and stomach than thosecapable of being created by self-expanding stent 11.

[0061] Referring now to FIG. 10, there is shown a sixth embodiment of astent adapted for use in draining a gastric pseudocyst in accordancewith the teachings of the present invention, said stent beingrepresented generally by reference numeral 201.

[0062] Stent 201, which is commonly referred to in the art as a doublepigtail stent, is a hollow member whose flexible ends 203-1 and 203-2are curled in their relaxed states but are adapted to be straightenedwhen a straightening force is applied thereto. Stent 201, which ispreferably made of a flexible plastic, has a fixed diameter of about10-11.5 Fr and a relaxed length of about 3-5 cm.

[0063] Referring now to FIGS. 11(a) and (b), there are shown fragmentaryside and fragmentary schematic longitudinal section views of a thirdembodiment of a stent delivery system constructed according to theteachings of the present invention, said stent delivery system beingrepresented generally by reference numeral 251.

[0064] System 251 comprises a flexible catheter 253. A handle 255 isdisposed at the proximal end of catheter 253, and a tip 257 is disposedat the distal end of catheter 253. A plurality of parallel lumens 259-1through 259-3 extend longitudinally through the distal end of catheter253. A guide wire 254 is removably received within lumen 259-1 and isadapted for use in positioning system 251 at a desired position within abody lumen. A retractable needle 256 (or retractable knife,sphincterotome or the like) is removably received within lumen 259-2 andis adapted for use in perforating the stomach and pseudocyst walls. (Itshould be noted that one of lumens 259-1 and 2592 could be eliminated,with needle 256 removably inserted therein and then guide wire 254removably inserted therein.) Lumen 259-3 is coupled at its proximal endto a line 260 containing a dye for use in performing a cystogram. Afourth lumen 261, which is connected at its proximal end to a gas line262, surrounds the distal ends of lumens 259-1 through 259-3 and ends ina balloon section 263 proximal to tip 257.

[0065] System 251 also comprises a pair of double pigtail stents 201-1and 201-2, said pigtail stents 201-1 and 201-2 being coaxially andslidably positioned over catheter 253 in an end-to-end arrangementproximal to balloon section 263. (Although in the present embodimentthere are two stents 201, it can readily be appreciated that there couldbe as few as one such stent or as many as three or more such stents.)

[0066] A pusher sleeve 265 coaxially surrounds catheter 253 proximal tostents 201-1 and 201-2. Pusher 265, which is adapted for axial movementrelative to catheter 253, has a handle 267 disposed at its proximal endfor use in axially moving pusher 265 relative to catheter 253. Pusher265 is adapted to engage the proximal end of stent 201-2 and to pushstents 201-1 and 201-2 off the distal end of catheter 253.

[0067] In use, system 251 is first endoscopically introduced into thepatient's stomach via the patient's mouth. Needle 256 is then used toperforate the stomach and the pseudocyst, respectively, and, thereafter,is retracted. Dye is transmitted through lumen 259-3, and a cystogram isperformed to confirm entry into a pseudocyst. Assuming that entry intopseudocyst is confirmed, guide wire 254 is then inserted through theperforations, and balloon section 263 is passed over guide wire 254.Balloon section 263 is then expanded to dilate the aforementionedperforations and, thereafter, is deflated. Stents 201-1 and 201-2 arethen sequentially pushed over the distal end of catheter 253 by pusher265 for implantation across the perforations to fluidly inteconnect thestomach and pseudocyst.

[0068] It is to be understood that the various stents described abovecould also be used in the surgical approach described above to drain apseudocyst to a point external to a patient's body, instead of drainingthe pseudocyst into the patient's stomach; however, such an approachwould suffer from the above-described shortcomings typically associatedwith invasive surgery.

[0069] The embodiments of the present invention recited herein areintended to be merely exemplary and those skilled in the art will beable to make numerous variations and modifications to it withoutdeparting from the spirit of the present invention. All such variationsand modifications are intended to be within the scope of the presentinvention as defined by the claims appended hereto.

What is claimed is:
 1. A method of draining a pseudocyst present withina patient, said method comprising the steps of: (a) providing a stent,said stent being transformable from a non-expanded state ofcomparatively lesser diameter to an expanded state of comparativelygreater diameter, said stent having a first end and a second end; (b)delivering said stent in said non-expanded state to a pseudocyst locatedwithin a patient; (c) inserting said first end of said stent into thepseudocyst; and (d) transforming said stent from said non-expanded stateto said expanded state; (e) whereby the pseudocyst drains through saidstent.
 2. The method as claimed in claim 1 further comprising the stepof inserting said second end of said stent into the stomach of thepatient whereby the pseudocyst drains through said stent into thestomach.
 3. The method as claimed in claim 2 further comprising, priorto said first end and second end inserting steps, forming a perforationin each of the pseudocyst and the stomach and wherein said first endinserting step comprises inserting said first end of said stent throughsaid perforations in the pseudocyst and the stomach.
 4. The method asclaimed in claim 1 wherein said stent is a self-expandable stent.
 5. Themethod as claimed in claim 4 wherein said delivering step comprisesmaintaining said stent in said non-expanded state using a removablerestraint and wherein said transforming step comprises removing saidremovable restraint from said stent to allow said stent to self-expand.6. The method as claimed in claim 4 wherein said delivering stepcomprises mounting said stent on the distal end of a catheter in saidnon-expanded state using a removable restraint and then inserting thedistal end of said catheter into a patient in the area of a pseudocyst.7. The method as claimed in claim 6 wherein said catheter inserting stepis performed intraorally using an endoscope.
 8. The method as claimed inclaim 4 wherein said stent is shaped to include a waist of comparativelylesser expanded diameter and a pair of cuffs on opposite ends of saidwaist of comparatively greater expanded diameter.
 9. The method asclaimed in claim 8 wherein said stent is made of a biocompatiblenonabsorbable material.
 10. The method as claimed in claim 8 whereinsaid stent is made of a biocompatible nonabsorbable polymeric material.11. The method as claimed in claim 8 wherein said stent is made of abioabsorbable material.
 12. The method as claimed in claim 8 whereinsaid waist has an expanded diameter of about 8-10 mm, each of said cuffshas an expanded diameter of about 15 mm, and wherein each of said waistand said cuffs has a length of about 5-10 mm.
 13. The method as claimedin claim 4 wherein said stent has a uniform expanded diameter.
 14. Themethod as claimed in claim 4 wherein said stent is made of a braidedfilamentary material.
 15. The method as claimed in claim 1 wherein saidstent is a balloon-expandable stent.
 16. The method as claimed in claim15 wherein said delivering step comprises mounting saidballoon-expandable stent, in said non-expanded state, over a deflatedballoon catheter and then inserting said deflated balloon catheter intoa patient in the area of a pseudocyst and wherein said transforming stepcomprises inflating said deflated balloon catheter until saidballoon-expandable stent is transformed from said non-expanded state tosaid expanded state.
 17. The method as claimed in claim 1 wherein saidstent is a balloon-expandable covered stent.
 18. The method as claimedin claim 17 wherein said delivering step comprises mounting saidballoon-expandable covered stent, in said non-expanded state, over adeflated balloon catheter and then inserting said deflated ballooncatheter into a patient in the area of a pseudocyst and wherein saidtransforming step comprises inflating said deflated balloon catheteruntil said balloon-expandable covered stent is transformed from saidnon-expanded state to said expanded state.
 19. The method as claimed inclaim 1 wherein said stent is nonabsorbable, said method furthercomprising the step of endoscopically removing said stent with a snareafter drainage of the pseudocyst is complete.
 20. A method of draining apseudocyst present within a patient, said method comprising the stepsof: (a) providing a double pigtail stent, said double pigtail stenthaving a first end and a second end, each of said first and second endsbeing transformable from a straightened state, when constrained, to acurled state, when relaxed; (b) coaxially mounting said double pigtailstent over the distal end of a catheter, whereby each of said first andsecond ends is in said straightened state; (c) endoscopicallyintroducing said double pigtail stent and the distal end of saidcatheter through the mouth and into the stomach of a patient in thevicinity of a pseudocyst; (d) sliding said first end of said doublepigtail stent off the distal end of said catheter, through the stomachand into the pseudocyst, whereby said first end is transformed from saidstraightened state to said curled state; and (e) sliding said second endof said double pigtail stent off the distal end of said catheter intothe stomach, whereby said second end is transformed from saidstraightened state to said curled state; (f) whereby the pseudocystdrains through said stent into the stomach.
 21. The method as claimed inclaim 20 further comprising, after said endoscopic introducing step andbefore said sliding steps, the step of forming a perforation in each ofthe stomach and the pseudocyst and wherein said first end sliding stepcomprises sliding said first end of said double pigtail stent off thedistal end of said catheter and through the perforations in the stomachand pseudocyst, respectively.
 22. The method as claimed in claim 21wherein the distal end of said catheter includes a balloon, said methodfurther comprising, after said perforation forming step and before saidsliding steps, the steps of inserting said balloon into saidperforations, then inflating said balloon, then deflating said balloonand withdrawing said balloon from said perforations.
 23. The method asclaimed in claim 20 further comprising the step of endoscopicallyremoving said double pigtail stent with a snare after drainage of thepseudocyst is complete.
 24. A stent delivery system comprising: (a) aninner catheter, said inner catheter being provided with a firstlongitudinally extending lumen; (b) perforating means slidably disposedin said first longitudinally extending lumen; (c) an outer catheter,said outer catheter surrounding at least a portion of the length of saidinner catheter and adapted for axial movement relative to said innercatheter; and (d) a self-expandable stent, said self-expandable stentdisposed between said inner catheter and said outer catheter; (e)wherein said outer catheter is dimensioned to maintain saidself-expandable stent in a compressed state.
 25. The stent deliverysystem as claimed in claim 24 wherein said self-expandable stent iscoaxially mounted over said inner catheter.
 26. The stent deliverysystem as claimed in claim 24 wherein said self-expandable stent is madeof braided filamentary material.
 27. The stent delivery system asclaimed in claim 24 wherein said self-expandable stent is made ofnonabsorbable material.
 28. The stent delivery system as claimed inclaim 24 wherein said self-expandable stent is made of nonabsorbableplastic material.
 29. The stent delivery system as claimed in claim 24wherein said self-expandable stent is made of bioabsorbable material.30. The stent delivery system as claimed in claim 24 wherein saidself-expandable stent has a uniform expanded diameter.
 31. The stentdelivery system as claimed in claim 24 wherein said self-expandable isshaped to include a waist of comparatively lesser expanded diameter anda pair of cuffs on opposite ends of said waist of comparatively greaterexpanded diameter.
 32. The stent delivery system as claimed in claim 31wherein said waist has an expanded diameter of about 8-10 mm, each ofsaid cuffs has an expanded diameter of about 15 mm, and wherein each ofsaid waist and said cuffs has a length of about 5-10 mm.
 33. The stentdelivery system as claimed in claim 24 wherein said perforating meanscomprises a retractable needle.
 34. The stent delivery system as claimedin claim 24 wherein said inner catheter is further provided with asecond longitudinal lumen, said stent delivery system further comprisinga guide wire slidably disposed in said second longitudinal lumen.
 35. Astent delivery system comprising: (a) a catheter, said catheter having aproximal end, a distal end, a first lumen extending longitudinallythrough said distal end and a second lumen extending longitudinally andhaving a proximal end connected to a gas line and a distal endterminating in a balloon section; (b) perforating means slidablydisposed in said first lumen; and (c) a balloon-expandable stentcoaxially mounted over said balloon section of said catheter.
 36. Thestent delivery system as claimed in claim 35 wherein saidballoon-expandable stent is a balloon-expandable covered stent.
 37. Thestent delivery system as claimed in claim 35 further comprising asheath, said sheath surrounding at least a portion of the length of saidcatheter and said balloon-expandable stent and being adapted for axialmovement relative to said catheter.
 38. The stent delivery system asclaimed in claim 35 wherein said perforating means comprises aretractable needle.
 39. The stent delivery system as claimed in claim 35wherein said catheter further comprises a third lumen extendinglongitudinally through said distal end and wherein said stent deliverysystem further comprises a guide wire slidably disposed in said thirdlumen.
 40. The stent delivery system as claimed in claim 39 wherein saidcatheter further comprises a fourth lumen extending longitudinallythrough said distal end, said fourth lumen being connected at itsproximal end to a line containing dye for use in performing a cystogram.41. A stent delivery system comprising: (a) a catheter, said catheterhaving a proximal end, a distal end, a first lumen extendinglongitudinally through said distal end, and a second lumen extendinglongitudinally and having a proximal end connected to a gas line and adistal end terminating in a balloon section; (b) perforating meansslidably disposed in said first lumen; and (c) a first pigtail stentcoaxially and slidably mounted over said catheter proximal to saidballoon section.
 42. The stent delivery system as claimed in claim 41further comprising a pusher sleeve coaxially and slidably mounted oversaid catheter proximal to said first pigtail stent for pushing saidfirst pigtail stent off said distal end of said catheter.
 43. The stentdelivery system as claimed in claim 41 further comprising a secondpigtail stent coaxially and slidably mounted over said catheter proximalto said balloon section and distal to said first pigtail stent.
 44. Thestent delivery system as claimed in claim 41 wherein said perforatingmeans comprises a retractable needle.
 45. The stent delivery system asclaimed in claim 41 wherein said catheter further comprises a thirdlumen extending longitudinally through said distal end and wherein saidstent delivery system further comprises a guide wire slidably disposedin said third lumen.
 46. The stent delivery system as claimed in claim45 wherein said catheter further comprises a fourth lumen extendinglongitudinally through said distal end, said fourth lumen beingconnected at its proximal end to a line containing dye for use inperforming a cystogram.